A method for calculating the flow during the run-up of a steam turbine generator set

Abstract

The application discloses a method for calculating the flow during the start-up of a steam turbine generator unit, and relates to a method for calculating the flow during the start-up. The application can accurately match the total energy consumption required during the start-up, prevents the excessive steam flow from causing the rapid increase of the rotating speed, shaft vibration, the over-temperature of the flow passage, or the insufficient flow from causing the failure of the start-up, the failure of maintaining the rotating speed, and guarantees the safety of the shaft, the cylinder, the bearing and other equipment during the whole start-up process; meanwhile, the flow is consistent with the theoretically calculated value, the established start-up curve can be strictly followed, the warm-up time and the speed-up time are shortened, and the start-up and stop efficiency of the unit is improved; meanwhile, the application is convenient for tracing the fault source, and when the start-up parameters are abnormal, the flow, equipment loss and other problem sources can be quickly distinguished. The application belongs to the technical field of steam turbine generator units and the calculation of the flow during the start-up.

Description

Technical Field

[0001] This invention relates to a method for calculating the initial flow rate, specifically a method for calculating the initial flow rate of a steam turbine generator set, belonging to the technical field of steam turbine generator sets and initial flow rate calculation. Background Technology

[0002] Start-up is the process of using high-pressure steam to impact the rotor blades and make the rotor rotate, and the start-up flow rate is one of the key parameters controlling this process. Appropriate start-up flow rate settings can shorten start-up time while ensuring safety, meeting the requirements of grid peak shaving and emergency rapid start-up. At the same time, optimizing steam consumption during the start-up phase is also an important aspect of energy conservation and consumption reduction for steam turbine units; reducing energy consumption during startup can improve overall operational economy.

[0003] Currently, the calculation methods for the initial flow rate of steam turbine generator sets still rely on the traditional Vlugel formula or proportional estimation method. However, these two calculation methods have the following problems in practical applications:

[0004] I. Freuger's Formula

[0005] The Freuger formula assumes that the flow area is constant, the steam flow is an ideal gas, the flow is a steady adiabatic flow, and the stage efficiency is constant. However, during the start-up phase, the turbine generator set is under extremely low load, the main steam valve is open at a small degree, the steam flow deviates from the design conditions, the stage efficiency changes significantly, the theoretical error of the formula increases significantly, and the exhaust pressure of the high-pressure cylinder does not approach 0 during the start-up phase, which further amplifies the error of the formula.

[0006] II. Proportional Estimation Method

[0007] General use on site ,in The steam flow rate at the main steam inlet of the steam turbine generator set under rated operating conditions is given by coefficient K, which is an empirical value (usually taken as 0.02 to 0.05). It has no quantitative boundary and does not distinguish between generator type, start-up status, start-up method, or bypass operation mode.

[0008] For units of the same capacity but from different manufacturers, or for the same unit in different conditions (new or old), using the estimation method may result in an overestimation of the flow rate (leading to thermal shock) or an underestimation of the flow rate (leading to insufficient warm-up and reheater overheating), and the accuracy cannot be guaranteed.

[0009] In summary, how to propose a novel method for calculating the flow rate to address the aforementioned technical problems has become a pressing issue for those skilled in the art. Summary of the Invention

[0010] To address the shortcomings of the prior art, this invention provides a method for calculating the initial flow rate of a steam turbine generator set.

[0011] The technical solution of this invention is: a method for calculating the initial flow rate of a steam turbine generator set, which specifically includes the following steps:

[0012] Step 1: Calculate the specific enthalpy of the steam at the steam inlet of the high-pressure cylinder. Enthalpy of exhaust steam at the low-pressure cylinder steam outlet ;

[0013] Step 2: Calculate the rotor speed-up loss power ;

[0014] Step 3: Calculate the heat transfer loss power between the rotor and stator. ;

[0015] Step 4: Calculate the rotor's frictional loss power. ;

[0016] Step 5: Calculate the work loss due to steam expansion. ;

[0017] Step 6: Calculate the starting flow rate Q:

[0018] .

[0019] Furthermore, The calculation method is as follows:

[0020]

[0021] In the formula:

[0022] Power loss due to rotor speed increase;

[0023] J is the rotor's moment of inertia;

[0024] α is the rotor angular acceleration;

[0025] N is the rotor speed per minute.

[0026] Furthermore, The calculation method is as follows:

[0027]

[0028] In the formula:

[0029] This refers to the power loss due to heat transfer.

[0030] c is the specific heat capacity of the metal;

[0031] m is the total mass of the stationary part and the rotor;

[0032] This represents the rate of change of temperature of the metal.

[0033] Furthermore, The calculation method is as follows:

[0034]

[0035] In the formula:

[0036] This refers to the power loss due to friction.

[0037] This refers to the power loss of the turbine bearings.

[0038] This is to reduce the power loss of the steam turbine blower.

[0039] This represents the power loss due to generator load.

[0040] Furthermore, The calculation method is as follows:

[0041]

[0042]

[0043]

[0044] In the formula:

[0045] Let i be the power loss of each radial bearing of the steam turbine, where i = 1, 2, 3…n, and n is a positive integer;

[0046] Let j be the power loss of each thrust bearing in the steam turbine, where j = 1, 2, 3…n, and n is a positive integer;

[0047] This refers to the dynamic viscosity of the lubricating oil.

[0048] Pi;

[0049] Let i be the inner diameter of each radial bearing of the turbine rotor, where i = 1, 2, 3…n, and n is a positive integer;

[0050] Let i be the effective width of each radial bearing of the turbine rotor, where i = 1, 2, 3…n, and n is a positive integer;

[0051] This refers to the rotor's revolutions per minute.

[0052] Let i be the radial clearance between the radial bearing radius and the corresponding rotor radius at each point on the turbine rotor, where i = 1, 2, 3…n, and n is a positive integer;

[0053] The friction coefficient of the turbine thrust bearing;

[0054] This represents the axial thrust borne by each thrust disc of the steam turbine, where j = 1, 2, 3…n, and n is a positive integer;

[0055] Let j be the diameter of each thrust disc of the steam turbine, where j = 1, 2, 3…n, and n is a positive integer.

[0056] Furthermore, The calculation method is as follows:

[0057]

[0058] In the formula:

[0059] The empirical coefficient for the low-pressure long blade blower of the steam turbine is taken as 0.0022~0.0032;

[0060] Let k be the average diameter of the outlet edge of each stage of the low-pressure turbine blades, where k = 1, 2, 3…n, and n is a positive integer;

[0061] Let k be the height of each stage of the low-pressure turbine blades, where k = 1, 2, 3…n, and n is a positive integer;

[0062] Let k be the circumferential velocity at the root of each stage of the low-pressure turbine blades, where k = 1, 2, 3…n, and n is a positive integer;

[0063] This refers to the exhaust steam specific volume at the steam outlet of the low-pressure cylinder.

[0064] Furthermore, The calculation method is as follows:

[0065]

[0066] This is the generator bearing loss coefficient, in KW / rpm;

[0067] This refers to the rotor's revolutions per minute.

[0068] This is the generator hysteresis loss coefficient, in KW / rpm;

[0069] This represents the generator eddy current loss coefficient, expressed in kWh / (rpm). 2 ;

[0070] This is the generator load loss factor, expressed in kW / (rpm). 2 ;

[0071] This is the generator load loss factor, expressed in kW / (rpm). 3 .

[0072] Furthermore, The calculation method is as follows:

[0073]

[0074] In the formula:

[0075] The work lost due to steam expansion;

[0076] The steam inlet pressure at the high-pressure cylinder steam inlet;

[0077] This refers to the exhaust pressure at the steam outlet of the low-pressure cylinder.

[0078] The specific volume of the steam inlet at the high-pressure cylinder steam inlet;

[0079] This refers to the exhaust steam specific volume at the steam outlet of the low-pressure cylinder.

[0080] Compared with the prior art, the present invention has the following advantages:

[0081] This invention proposes a precise method for calculating the steam flow rate during the start-up of a steam turbine generator set, which has multiple engineering benefits:

[0082] 1. Safety aspect: During the start-up process of the steam turbine generator set, the steam energy of the start-up flow needs to bear the rotor acceleration kinetic energy, metal heat transfer loss, bearing / blower / generator friction power consumption and steam expansion power consumption; therefore, this invention can accurately match the total energy consumption required for the start-up, prevent excessive steam flow from causing the speed to soar, shaft vibration, and overheating of the flow passage, or insufficient flow from causing start-up failure and inability to maintain the speed, thus ensuring the safety of the shaft system, cylinder, bearings and other equipment throughout the start-up process.

[0083] 2. Equipment lifespan: Precise quantity control can stabilize steam parameters and temperature rise rate, reduce thermal stress and thermal deformation of thick-walled metal components such as rotors and cylinders, slow down fatigue damage, and effectively extend the service life of the unit and auxiliary equipment.

[0084] 3. Economic aspects: Supplying steam on demand eliminates the waste of steam, condensate and auxiliary equipment power caused by blindly rushing large flow rates, and significantly reduces the overall energy consumption during the start-up and shutdown of the unit.

[0085] 4. Operation and control level: The flow rate closely matches the theoretical calculation value, which can strictly follow the established start-up curve, shorten the warm-up and speed-up time, and improve the start-up and shutdown efficiency of the unit; at the same time, it facilitates fault tracing. When the start-up parameters are abnormal, the root cause of problems such as flow rate and equipment loss can be quickly identified. Attached Figure Description

[0086] Figure 1 This is the first data graph of steam parameters and spooling flow rate Q in this invention. When the steam parameters (pressure and temperature) are set to constant values, the spooling flow rate Q required for the turbine generator set to spool to the operating speed is selected according to the data graph.

[0087] Figure 2 This is the second data graph of steam parameters and starting flow rate Q in this invention. When the starting flow rate Q is a fixed value, the steam parameters (pressure and temperature) required for the turbine generator set to start up to the working speed are selected according to the data graph. Detailed Implementation

[0088] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments.

[0089] Specific implementation method one: Combining Figures 1 to 2 This embodiment describes a method for calculating the initial flow rate of a steam turbine generator set. The method is specifically performed according to the following steps:

[0090] Step 1: Calculate the specific enthalpy of the steam at the high-pressure cylinder inlet using the IAPWS-IF97 formula. Enthalpy of exhaust steam at the low-pressure cylinder steam outlet ;

[0091] Step 2: Calculate the rotor speed-up loss power ;

[0092] Step 3: Calculate the heat transfer loss power between the rotor and stator. ;

[0093] Step 4: Calculate the rotor's frictional loss power. ;

[0094] Step 5: Calculate the work loss due to steam expansion. ;

[0095] Step Six: Utilize , , , , and Calculate the flow rate Q (in tons per hour):

[0096] .

[0097] Specific Implementation Method Two: Combining Figures 1 to 2 This embodiment describes the implementation method. The calculation method is as follows:

[0098]

[0099] In the formula:

[0100] This represents the power loss due to rotor speed increase, expressed in kW.

[0101] J is the rotor's moment of inertia, measured in kg·m. 2 ;

[0102] α is the rotor angular acceleration, with units of rad / s. 2 ;

[0103] N represents the rotor's revolutions per minute, measured in rpm.

[0104] The other components and connections are the same as in Specific Implementation Method 1.

[0105] Specific implementation method three: Combining Figures 1 to 2 This embodiment describes the following: The calculation method is as follows:

[0106]

[0107] In the formula:

[0108] This represents heat transfer loss power, measured in kW.

[0109] c is the specific heat capacity of the metal, expressed in J / (kg·℃);

[0110] m is the total mass of the stationary components and the rotor, in kg;

[0111] This represents the rate of temperature change of the metal, expressed in °C / min.

[0112] The other components and connections are the same as in specific implementation method one or two.

[0113] Specific implementation method four: Combination Figures 1 to 2 This embodiment describes the implementation method. The calculation method is as follows:

[0114]

[0115] In the formula:

[0116] This refers to the power loss due to friction, expressed in kW.

[0117] This refers to the power loss of the turbine bearings, expressed in kW.

[0118] This refers to the blower power loss of the steam turbine, expressed in KW.

[0119] This represents the generator load loss power, expressed in kW.

[0120] Furthermore, The calculation method is as follows:

[0121]

[0122]

[0123]

[0124] In the formula:

[0125] The power loss of each radial bearing in the steam turbine is expressed in kW; where i = 1, 2, 3…n, and n is a positive integer.

[0126] The power loss of each thrust bearing in the steam turbine is expressed in kW; where j = 1, 2, 3…n, and n is a positive integer.

[0127] This refers to the dynamic viscosity of the lubricating oil, in units of... ;

[0128] Pi;

[0129] Let i be the inner diameter of each radial bearing of the turbine rotor, in meters (m), where i = 1, 2, 3…n, and n is a positive integer.

[0130] The effective width of each radial bearing of the turbine rotor is given in meters (m), where i = 1, 2, 3…n, and n is a positive integer.

[0131] This refers to the rotor's revolutions per minute, expressed in rpm.

[0132] The radial clearance between the radial bearing radius and the corresponding rotor radius at various points on the turbine rotor is expressed in meters (m); where i = 1, 2, 3…n, and n is a positive integer.

[0133] The friction coefficient of the turbine thrust bearing is taken as 0.0015~0.0025;

[0134] This represents the axial thrust borne by each thrust plate of the steam turbine, expressed in N; where j = 1, 2, 3…n, and n is a positive integer;

[0135] denoted as the diameter of each thrust disc of the steam turbine, in meters; where j = 1, 2, 3…n, and n is a positive integer.

[0136] Furthermore, The calculation method is as follows:

[0137]

[0138] In the formula:

[0139] The empirical coefficient for the low-pressure long blade blower of the steam turbine is taken as 0.0022~0.0032;

[0140] denoted as k, which is the average diameter of the outlet edge of each stage of the low-pressure turbine blades, in meters; where k = 1, 2, 3…n, and n is a positive integer.

[0141] The height of each stage of the low-pressure turbine blades is expressed in meters (m); where k = 1, 2, 3…n, and n is a positive integer.

[0142] denoted as k, which is the circumferential velocity at the root of each stage of the low-pressure turbine blades, in m / s; where k = 1, 2, 3…n, and n is a positive integer;

[0143] The exhaust steam specific volume at the low-pressure cylinder steam outlet, in cubic meters per second (m³). 3 / kg.

[0144] Furthermore, The calculation method is as follows:

[0145]

[0146] This is the generator bearing loss coefficient, in KW / rpm;

[0147] This refers to the rotor's revolutions per minute, expressed in rpm.

[0148] This is the generator hysteresis loss coefficient, in KW / rpm;

[0149] This represents the generator eddy current loss coefficient, expressed in kWh / (rpm). 2 ;

[0150] This is the generator load loss factor, expressed in kW / (rpm). 2 ;

[0151] This is the generator load loss factor, expressed in kW / (rpm). 3 .

[0152] The other components and connections are the same as those in specific implementation methods one, two, or three.

[0153] Specific Implementation Method Five: Combining Figures 1 to 2 This embodiment describes the implementation method. The calculation method is as follows:

[0154]

[0155] In the formula:

[0156] This represents the work lost due to steam expansion, measured in kJ / kg.

[0157] This is the steam inlet pressure at the high-pressure cylinder, expressed in MPa.

[0158] This is the exhaust pressure at the steam outlet of the low-pressure cylinder, in MPa.

[0159] The specific volume of steam at the inlet of the high-pressure cylinder is expressed in cubic meters (m³). 3 / kg;

[0160] The exhaust steam specific volume at the low-pressure cylinder steam outlet, in cubic meters per second (m³). 3 / kg.

[0161] The other components and connections are the same as those in specific implementation methods one, two, three, or four.

[0162] The present invention has been disclosed above with reference to preferred embodiments, but it is not intended to limit the present invention. Any simple modifications, equivalent changes and alterations made by those skilled in the art to the above embodiments without departing from the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for calculating the initial flow rate of a steam turbine generator set, characterized in that: This method is specifically carried out in the following steps: Step 1: Calculate the specific enthalpy of the steam at the steam inlet of the high-pressure cylinder. Enthalpy of exhaust steam at the low-pressure cylinder steam outlet ; Step 2: Calculate the rotor speed-up loss power ; Step 3: Calculate the heat transfer loss power between the rotor and stator. ; Step 4: Calculate the rotor's frictional loss power. ; Step 5: Calculate the work loss due to steam expansion. ; Step 6: Calculate the starting flow rate Q: 。 2. The method for calculating the initial flow rate of a steam turbine generator set according to claim 1, characterized in that: In step two The calculation method is as follows: In the formula: Power loss due to rotor speed increase; J is the rotor's moment of inertia; α is the rotor angular acceleration; N is the rotor speed per minute.

3. The method for calculating the initial flow rate of a steam turbine generator set according to claim 2, characterized in that: In step three The calculation method is as follows: In the formula: This refers to the power loss due to heat transfer. c is the specific heat capacity of the metal; m is the total mass of the stationary part and the rotor; This represents the rate of change of temperature of the metal.

4. The method for calculating the initial flow rate of a steam turbine generator set according to claim 3, characterized in that: In step four The calculation method is as follows: In the formula: This refers to the power loss due to friction. This refers to the power loss of the turbine bearings. This is to reduce the power loss of the steam turbine blower. This represents the power loss due to generator load.

5. The method for calculating the initial flow rate of a steam turbine generator set according to claim 4, characterized in that: The The calculation method is as follows: In the formula: Let i be the power loss of each radial bearing of the steam turbine, where i = 1, 2, 3…n, and n is a positive integer; Let j be the power loss of each thrust bearing in the steam turbine, where j = 1, 2, 3…n, and n is a positive integer; This refers to the dynamic viscosity of the lubricating oil. Pi; Let i be the inner diameter of each radial bearing of the turbine rotor, where i = 1, 2, 3…n, and n is a positive integer; Let i be the effective width of each radial bearing of the turbine rotor, where i = 1, 2, 3…n, and n is a positive integer; This refers to the rotor's revolutions per minute. Let i be the radial clearance between the radial bearing radius and the corresponding rotor radius at each point on the turbine rotor, where i = 1, 2, 3…n, and n is a positive integer; The friction coefficient of the turbine thrust bearing; This represents the axial thrust borne by each thrust disc of the steam turbine, where j = 1, 2, 3…n, and n is a positive integer; Let j be the diameter of each thrust disc of the steam turbine, where j = 1, 2, 3…n, and n is a positive integer.

6. The method for calculating the initial flow rate of a steam turbine generator set according to claim 5, characterized in that: The The calculation method is as follows: In the formula: The empirical coefficient for the low-pressure long blade blower of the steam turbine is taken as 0.0022~0.0032; Let k be the average diameter of the outlet edge of each stage of the low-pressure turbine blades, where k = 1, 2, 3…n, and n is a positive integer; Let k be the height of each stage of the low-pressure turbine blades, where k = 1, 2, 3…n, and n is a positive integer; Let k be the circumferential velocity at the root of each stage of the low-pressure turbine blades, where k = 1, 2, 3…n, and n is a positive integer; This refers to the exhaust steam specific volume at the steam outlet of the low-pressure cylinder.

7. The method for calculating the initial flow rate of a steam turbine generator set according to claim 6, characterized in that: The The calculation method is as follows: This refers to the generator bearing loss coefficient. This refers to the rotor's revolutions per minute. This is the generator hysteresis loss coefficient; The generator eddy current loss coefficient; This is the generator load loss coefficient; This is the generator load loss coefficient.

8. The method for calculating the initial flow rate of a steam turbine generator set according to claim 7, characterized in that: In step five The calculation method is as follows: In the formula: The work lost due to steam expansion; The steam inlet pressure at the high-pressure cylinder steam inlet; This refers to the exhaust pressure at the steam outlet of the low-pressure cylinder. The specific volume of the steam inlet at the high-pressure cylinder steam inlet; This refers to the exhaust steam specific volume at the steam outlet of the low-pressure cylinder.

9. The method for calculating the initial flow rate of a steam turbine generator set according to claim 1, characterized in that: In step one, the exhaust vapor enthalpy is calculated using the IAPWS-IF97 formula. .

10. The method for calculating the initial flow rate of a steam turbine generator set according to claim 9, characterized in that: In step one, the exhaust vapor enthalpy is calculated using the IAPWS-IF97 formula. .

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